An image forming apparatus usually prints an image such as letters or the like on a recording face of a recording sheet while conveying the recording sheet on a conveying path set in the image forming apparatus (or a casing thereof). If the recording sheet passes through a curved conveying path, the recording sheet may have a bending tendency (or a curl).
Therefore, the bending tendency is offset and eliminated usually by curving the recording sheet in a direction opposite to the bending tendency. As specific means for curving the recording sheet in a direction opposite to the bending tendency, there is known an uncurling mechanism, which includes a conveying roller and a pair of follower rollers arranged along a circumference direction of the conveying roller and confronting the conveying roller.
In this uncurling mechanism, the pair of follower rollers winds the recording sheet on the conveying rollers so that the recording sheet is curved in the direction opposite to the bending tendency thereby to offset and remove the bending tendency.
However, different recording sheets have different warping rigidity and different bending tendency in accordance with their kinds. Thus, the bending tendency of all kinds of the recording sheets may not be properly cleared if they are forcibly curved under a common condition.
JP-A-6-183628 discloses a configuration in which a pair of follower rollers are integrated by a support plate or the like, and the support plate is moved in parallel with the conveying direction of the recording sheet. The Support plate is moved such that one of the pair of follower rollers is brought into contact with the recording sheet on the conveying roller in one case, and the one of the follower rollers is separated from the recording sheet in another case. Thus, various kinds of recording sheets can be dealt with.
JP-A-8-175733 discloses a configuration in which the follower roller on the upstream side in the conveying direction is moved in parallel with a direction perpendicular to the conveying direction such that the follower roller is brought into and out of contact with the recording sheet on the conveying roller, so that various kinds of recording sheets can be dealt with.